Galileo and the speed of light

What the Activity is for

This activity involves telling a story, which you can use as a means of starting a discussion about the role of measurement in science, here relating ideas to evidence.

What to Prepare

• a copy of the story and possibly a portrait of Galileo projected onto a white board (see below)

What Happens During this Activity

There are various ways in which you might draw on this story. You might simply tell it as a story and engage the pupils in discussion around the kinds of questions listed below. Alternatively you might use the text for a class reading and comprehension exercise. First of all the class read through the passage, then the pupils work in pairs to talk through the questions and make notes about their responses. Pairs of pupils then report back in whole-class discussion.

Questions for talking through with your class:

• What do you think Galileo wrote down as his conclusion for the experiment?
• What do you think the pattern (the more recordings taken, the shorter the measured time) in Galileo's results suggested to him?
• What does the pattern in Galileo's results suggest to you? How could you support your suggestion?
• What was the big problem which Galileo faced with his experiment?
• Would it be possible to use this kind of direct measurement approach to find the speed of sound?

The speed of light is huge, but was measured before we had clocks to time very short intervals. Further research could focus on the questions: So how could the measurement be made? and How was it done?